There are a variety of techniques for pumping fluids from underground reservoirs. Over a hundred years ago, general windmill and hand pump systems were developed to access well water for drinking and irrigation. Oil well piston pumps with top head pump jacks were also developed to recover oil. These devices used top head drive piston pumps and stand pipes for the fluid discharge. This basic technology, albeit in more advanced forms, is in use today. Of course today, pumping systems are used in a variety of applications and come in a variety of other forms as well.
Both the water well and oil well top head drive piston pumps had to address the problem of liquid discharge of liquid at the surface. The liquid discharge needs to be directed and pumped. Many modern pumping techniques, for example, are called upon to pump underground fluid in a liquid sealed manner. This is particularly useful because in many applications, such as leachate removal from a landfill, oil and tar removal from petroleum or chemical facilities and clean up of remediation sites, tank farms, pipe lines, manufactured glass plant (MGP) sites, and caisson sumps, the fluids being pumped can be hazardous to people and the environment. As a result, it is desirable to have a pumping system that prevents leakage.
To prevent leakage, water well and oil well piston pump systems use a stuffing box mounted near the top of the ground seal for the well. Stuffing box systems use a positive displacement drive rod piston to pump fluid into a discharge tee that channels the liquid to a desired location, such as a collection area or processing unit. Because this pumping can be against substantial back pressure, the stuffing box acts to counter this back pressure and direct the discharge through the discharge tee. The stuffing box forms a tight seal above the discharge tee and around the reciprocating drive rod to prevent pumped fluid from spilling on the reciprocating rod drive mechanism or seeping around the reciprocating drive rod onto the ground.
Current stuffing box designs, however, fail to give long enough liquid sealing life. The stuffing box packing seal material is constantly being worn away causing leakage and the need to constantly tighten down on the packing gland jam nut squeezing the surrounding packing material around the drive rod to stop leakage. This especially occurs where pumps are used to pump against substantial back pressure (liquid head pressure) and where pumps are used to pump fluid with substantial amounts of grit or other contaminants.
Current packing gland stuffing box designs suffer from short sealing life. For example, stuffing boxes that use packing gland design and packing materials for sealing are problematic because of the constant need to compress the packing material down against the reciprocating drive rod. In these devices, materials like graphite impregnated twine (plumber's oakum) or slant cut split rubber o-rings are slipped around the drive rod and used as the packing material, screwed down in the stuffing box by a packing gland nut to create a liquid tight seal against the drive rod. The packing material has to be compressed just right to form a tight seal, however. If the material is too compacted, the material may squeeze against the drive rod and cause stalling of the pumping system. If the packing material is too loose, fluid leakage will occur.
In other words, for the stuffing box to work, packing material needs to be in a certain operational range. This optimization can be difficult to achieve even during the initial installation, but even more problematic, is that movement of the drive rod will affect the amount of packing on the packing material. The reciprocating action of the sucker rod in the riser pipe will wear away the packing material, unpacking the material around the drive rod necessitating tightening the packing gland to confine the packing material or replacement of the stuffing box packing material or finding some way of re-packing the packing material into the desired, operable range.
With current stuffing box designs, there is also no mechanism to identify a seal failure before failure occurs on the stuffing box, and open leakage occurs. If the packing material is no longer in the desired, operable range, the stuffing box will start to leak and can cause environmental or physical damage before the leaking is even detected. It is desirable, therefore, to have a stuffing box that can provide some pre-indication of such leakage.
A problem with current u-cup stuffing box design is alignment. In particular, when the seals of a stuffing box begin to fail, fluid leakage can occur. In such circumstances it is quite difficult to replace the stuffing box, because the entire stuffing box must be removed from the pump motor frame in order to replace its failed internal seals, seals which have likely corroded or degraded and thus no longer seal against the drive rod. Furthermore, unless the drive motor frame and the stuffing box seal are properly aligned upon replacement, then not only could the stuffing box seals fail more quickly, but misalignment could cause premature failure of the expensive, pneumatic drive motor air cylinder.